Insect damage to tempera painting

I am writing because I have been presented with two contemporary
tempera paintings (Sennelier paints and medium) on clayboard panels
that present what appears to be insect damage on the painted
surface.  I have posted four sets of images to my DropBox account,
which can be accessed at:

    <URL:https://www.dropbox.com/sh/eiq9tfiwwlrhlgx/AAAA-jw-EGvvV-ktHKkCjtn0a?dl=0>

I have never encountered such a condition before.  So before
considering treatment I would like, as best as possible, to
confirm/establish the cause of the observed damage.  So I pose two
sets of questions to the community:

Has anyone ever encountered insect damage to the painted surface of
tempera paintings on panel?  Images would be greatly appreciated.
How was the cause of damage determined and confirmed?

What else might account for the type of damage observed?  Has anyone
ever encountered similar conditions firmly attributed to an
alternative cause?

I might mention that the damage emerged only upon the painting's
concurrent arrival at their present location from different points
of origin and progressed very rapidly over the course of a week
while they were both in the same climate-controlled basement storage
facility.  Progress appears to have halted once the paintings were
either isolated (by carefully sealed wrapping) or removed from that
location.  I would further mention that one painting is over a year
old and presented no evidence of such damage upon arrival; while the
other was only completed by the artist within a week of its arrival.

Thanks in advance for any light any one may be able to shed on this
unusual--unique in my experience--damage/condition.

Steven Prins
Steven Prins and Company
Conservation and Restoration of Paintings
1570 Pacheco, Suite D-4
Santa Fe NM 87505-3986
505-983-2528


                                  ***
                  Conservation DistList Instance 30:7
                  Distributed: Saturday, July 2, 2016
                        Message Id: cdl-30-7-018
                                  ***